Photographic hardening developer



Patented Aug. 31, 1937 UNITED- STATES PATENT OFFICE PHOTOGRAPHIC HARDENING DEVELOPER Jersey No Drawing. Application April 2, 1935,

Serial No. 14,373

7 Claims. ((31. 95-88) This invention relates to photographic hardening developing baths and particularly to such baths containing compounds of boron. v

The development of photographic films or plates is usually carried out at temperatures of or F. and at these temperatures there is little tendency for the gelatin to soften and swell to an injurious extent during the development. When developing at higher temperatures, which procedure is. sometimes resorted toin order to decrease the time of development or because cold water for the developer solution is not available, as in development in warm climates, this tendency for the gelatin to soften and swell is greatly increased. In order to prevent this swelling, a gelatin hardener must be used either immediately after the plate or film is removed from the developer solution or preferably as a constituent of the developer bath. While it has been known to add a hardener directly to the'developer bath, such practice has not been satisfactory. Hardening developers have been compounded with chrome alum as the hardening agent, and 2,4- diaminophenol as the developing agent. Formaldehyde has also been added to various developer formulas. The degree of hardening of the chrome alum formulas decreases rapidly with the age of the bath, and in the formaldehyde formulas the developing agents oxidize readily. Potassium alum sludges when compounded in formulas similar to those used with chrome alum.

Accordingly,.the principal object of this invention is to produce a hardening developing bath having increased hardening life and decreased sludging tendency. A further object is to produce a hardening developing bath which does not give oil an objectionable odor on use.

These objects are accomplished according to my invention by adding a boron compound, an acid such as acetic, propionic or butyric or their soluble salts, and a hardening agent to the developer.

In preparing a developer, in .accordance with my invention, the baths may be prepared as two or more solutions or as a single solution. The essential ingredients include a developing agent, a preservative for the developing agent; such as sodium sulfite a hardening agent, and compounds which prevent the precipitation of the hardening agent. Compounds which prevent the precipitation of potassium alum include all of the oxygent acids or boron or their soluble salts in combination with acids or their soluble salts, such as acetic acid, propionic acid, or butyric acid.

Small quantities of acids or their soluble salts such as citric, tartaric, glycerophosphoric, lactic, etc. may also be added to prevent the precipitation of the alum. Large quantities of these acids tend to decrease the hardening action of the alum. The following examples will serve to illustrate developer solutions made in accordance with my invention:

EXAMPLE I Solution A 2,4-diamino phenol dihydrochloride grams 10 In each case, add'Solution A to Solution B.

' The following single solution developer can be readily mixed at temperatures less than F. ii the chemicals are dissolved in the order given:

Water cc 500, 2,4-diaminophenol dihydrochloride grams 11.25

Sodium sulflte (desiccated) do 22.5 Sodium metaborate 8H2O d0 7.5 to 30 Boric acid do 7.5 Sodiumacetate(anhydrous) do 30.0 Alum do 30.0 Water to liter 1.0

Thirty grams per liter of sodium metaborate produces the most active developer which can be compounded with the above formula.

,The boron compounds and s dium acetate present in these developers overcome sludging by preventing precipitation of the alum and, since precipitation of the alum is prevented, the hardening life of the developer is thereby increased.

These developers have a neutral or slightly acid reaction. The developing agents which may be employed include those which develop in solutions in which the pH value is 7 or slightly less, The

developer used in the above examples, 2,4-diamino phenol dihydrochloride, is a typical example of a developer which functions at a pH of 5 to 7. Monomethyl-para-aminophenol sulphate may also be used, but it is less active.

The borax or the sodium metaborate may be replaced in the formulas given by any compound which furnishes the borate ion in solution, such as a soluble oxygen acid of boron or its soluble salt. If this change is made in the formula, the rest of the formula must also be changed to compensate for the changed alkalinity, so that the solution has the proper hydrogen ion concentration of '7 or slightly less.

The hardening agent may be potassium alum or any other suitable aluminum salt which produces hardening and has the desired non-sludging property. Chrome alum is not a suitable hardener for use in these developers.

The sodium acetate may be replaced by any soluble compound such as sodium propionate or butyrate' which furnishes in solution suflicient acetate ions or other organic anions to prevent sludging.

The hardening developing solutions produced in accordance with my invention will function at various temperatures. At 65 F. a very long time is required for the development and the developer, while suitable for use at this temperature, is not very practical. At 85 F., using the formulas given in the above examples, the time required for the development is between ten and thirty minutes; When the developer is used at temperatures above 90 F., it is desirable to add about 5% of anhydrous sodium sulphate to the solution to prevent swelling of the gelatin layer of the film. The developers may be used at temperatures as high as 130 F., but at these high temperatures an acid hardening fixing bath is desirably used and, in some cases, is necessary. Such an acid hardening fixing bath is disclosed in my prior U. S. Patent No. 1,981,391.

Developers made in accordance with my invention do not give off an objectionable odor of sulfur dioxide when they are used, due to the fact that the pH is too great to permit the formation of this gas. In more acid solutions, sulfur dioxide is frequently evolved, and is a source of annoyance and trouble.

I have referred above to "soluble oxygen acid of boron and its soluble salts. The salts referred to may include the inorganic true salts and also the organic compounds or esters derived from these acids.

Developer solutions containing other ingredients and proportions of agents may be made in accordance with the above disclosure and I consider my invention as limited only by the terms of the appended claims.

WhatI claim is:

1. A photographic hardening developer comprislng a developing agent, an aluminum alum, a compound which furnishes in solution a watersoluble aliphatic" acid anion, and a compound which furnishes in solution a borate ion, the last mentioned compound being present in the amount of approximately 7.5 grams to approximately 30 grams per liter of developing solution, and the developer having a pH of less than 7.

2. A photographic hardening developer comprising a developing agent, an aluminum alum, a compound which furnishes in solution a watersoluble aliphatic acid anion, and boric acid in the amount of approximately 7.5 grams to approximately 30 grams per liter of developing solution, the developer having a pH of less than 7.

3. A photographic hardening developer comprising a developing agent, an aluminum alum, a compound which furnishes in solution a watersoluble aliphatic acid anion, and a metaborate in the amount of approximately 7.5 grams to approximately 30 grams per liter of developing solution, the developer having a pH of less than 7 4. A photographic hardening developer comprising a developing agent, an aluminum alum, a compound which furnishes in solution a Watersoluble aliphatic acid anion, and borax in the amount of approximately 7.5 grams to approximately 30 grams per liter of developing solution, the developer having a pH of less than 7.

5. A photographic hardening developer comprising 2,4-diamino phenol dihydrochloride, an aluminum alum, a compound which furnishes in solution a water-soluble aliphatic acid anion, and

'borax in the amount of approximately 7.5 grams to approximately 30 grams per liter of developing solution, the developer having a pH of about 5 to about 7.

6. A photographic hardening developer comprising approximately 10 .grams per liter of a developing agent, approximately 20 to 30 grams per liter of an aluminum alum, approximately 20 to 30 grams per liter of a compound which furnishes a water-soluble aliphatic acid anion in solution, and approximately 7.5 to 30 grams per liter of a compound which furnishes a borate ion in solution.

7. A photographic hardening developer comprising approximately 10 grams per liter of a developing agent, approximately 20 to 30 grams per liter of an aluminum alum, approximately 20 to 30 grams per liter of sodium acetate, and approximately 7.5 to 30 grams per liter of a metaborate.

HAROLD D. RUSSELL. 

